Edited texture not replacing old texture in render
No programming required to paint in blender. :)

It looks to me like you simply did not save your image after you painted it.

Blender will display the changed image in the viewport, but until you save it blender will not render it (and your work will be lost if you close blender, even after CtrlS).

With the mouse in the UV/Image Editor press AltS, or from the header Image > Save Image. That writes the changes you made in blender to an image file, actually saving your image. Now your render will look as excepted.



Here is an animated gif showing me painting on an object in the 3D view, then rendering it without saving the edited image.